Preclinical experiments on frozen chondrocytes derived from articular cartilage were performed for their transplantation for repair of articular cartilage defects in osteoarthritis.Experiment 1. Animal chondrocytesChondrocytes obtained from young female swine were isolated and kept frozen at -196℃ for various periods of time. Effects of the length of cryopreservation on the rate of viable cells and their ability to synthesize proteoglican (PG) and collagen were studied. Effects of various growth factors were assessed by keeping the cells frozen for one of them. The results are as follows :1) The rates of viable cells in the cells kept frozen for 2 weeks or less and further up to 12 weeks were 90% and 80%, respectively.2) The frozen chondrocytes were not significantly different from unfrozen chondrocytes in ability to synthesize PG and collagen, regardless of the duration of freezing, whether they were kept frozen for 2, 4, 8 or 12 weeks.3) Growth factors such as TGF-β, IGF-1 and bFGF invariably increased the abilities to synthesize PG and collagen even in cells kept frozen for as long as 12 weeks.Experiment 2. Human chondrocytesAfter patient's agreement, cartilages were collected from femoral heads excised during operations for femoral neck fractures. The results are as follows :1) The rates of viable cells were 82.7%, 80.7% and 78.2% in the cells kept frozen for 2 or less, 4 and 8 weeks, respectively.2) The abilities to synthesize PG and collagen showed no significant change even in cells kept frozen for further up to 8 weeks.3) Growth factors (TGF-β, IGF-1 and bFGF) increased the abilities to synthesize PG and collagen. The increased abilities remained unchanged even in the cells kept frozen for 8 weeks.In brief, the chondrocytes kept frozen for as long as 8 to 12 weeks were considered transplantable.